We didn't move Isabella (dd1) to a big bed until she was around 3 and we had lots and lots of issues when we did it and it was a matter of her getting used to it, which took a while
. She was coming out of the bed, waking up at night and coming to us, waking up at a silly time in the morning (4.30am).... all of which we dealt with as best as we could (silent return to bed, offer earlier bedtime). With Jasmine (dd2), I kept her in the cot until she was 4
and to be honest, the transition was a lot smoother than with Isabella and she just never came out... might have to do with their personalities and Isabella is a very spirited little girl! Jasmine was fine in her cot until then and I just didn't see the need to get her into a bed. She knew how to climb over the cot but she hardly ever did it and she knew how to climb, turn herself over and hop down but she didn't start doing that until she was way past 3.
I also put a gate by the door and Isabella would get out of her bed and fall asleep by the gate and then she started jumping over the gate so we just took it off as it defeated the purpose! I had to stay with her many many nights to get her to settle down as she was getting herself so worked up and kept coming out and we did some gradual withdrawal (sat by her bed and moved towards the door every couple of days). What also helped was to ask her to stay in her bed and tell her I would be back to check on her in x amount of time (you could start with 30 secs) and then come back and then with time increase that to say 1 min and come back again. But honestly, it took us a very long time to get to this stage (again i think because of her very spirited nature lol).
Its not uncommon for them to resist naps when there's a newborn in the house. He might have had nap troubles due to the timing of the nap or he just needs more mummy time before he goes down for a nap time?
Here are a couple of links that may help you:
The Crib to Bed TransitionSuccess Stories for Big Bed Transitions (please post link here)HTH